Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare openWorldHint, non-destructive, non-idempotent, and readOnlyHint=false. The description adds substantial behavioral detail beyond them: default 1-credit cost, platform-specific credit rates, and precise conditions under which charges are or are not incurred. The main omission is any note on authentication requirements or rate limits.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The first sentence is front-loaded and effective, but the description then repeats the long URL-family list already present in the schema and continues into pricing details. It is substantially longer than necessary and duplicates structured data rather than concentrating on value-add information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The tool has an output schema, full parameter schema coverage, and annotations covering safety and openness. The description completes the picture with supported input families, credit pricing, and charge-exemption rules, so an agent has enough information to call it correctly without relying on omitted return-value explanations.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the single URL parameter is already fully documented in the schema. The description duplicates the same supported URL-family text rather than adding new parameter meaning, so the baseline of 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The first sentence states a specific verb and resource: return downloadable image, video, and audio URLs from a supported public single-post URL. It also scopes the tool to public single-post inputs and enumerates supported URL families, so an agent can identify the operation without ambiguity.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives clear applicability through the extensive supported URL-family list and states that unsupported URLs are not charged. It lacks explicit when-not-to-use guidance beyond unsupported URLs, but there are no sibling tools to route between, so the usage context is still strong.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.